Maybe "boot pulls" is more proper. Here are some more examples. Based on the asymmetry of the cutouts, one of yours probably had a button hook as well like in these sets.

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Name: 782337868ad81f72db43cd8eb7210000--pulls-th-century.jpg Views: 144 Size: 27.4 KB

Name: using-boot-hooks.jpg Views: 135 Size: 7.6 KB